I. Our preliminary data suggests that differences in gene expression in the canonical circadian clock genes do not explain the long circadian period we observed in both male and female flies. We are therefore in the process of identifying potential candidate genes using RNA-Seq. Transcriptome profiles have been established for males and females of the long period line, and compared to flies having a normal circadian period. We measured gene expression across twelve time points in order to identify differences in cycling across a normal 24-hour day. We have frozen three replicates of 150 heads for each time point, sex, and genotype under dark:dark conditions. We have sequenced the RNA of these 144 samples. II. To identify genes with differences between the long period line and the normal period line, we first used a linear model to discern which genes were differentially expressed with respect to genotype and time. Those genes that were differentially expressed with respect to time were analyzed further using both JTK-Cycle and RAIN. These programs can be used to detect cycling gene expression. We are following up on the candidate genes identified using these programs.